1. Field of the Invention
The present invention relates to an image forming apparatus of tandem type which includes a plurality of photoreceptors disposed along a linearly extending sheet transportation path.
2. Description of Related Art
In recent years, color image forming apparatuses of tandem type have been provided in which four photoreceptor drums respectively adapted to form cyan, magenta, yellow and black monochromatic toner images are disposed in series along a linearly extending sheet transportation path.
In such a tandem color image forming apparatus, the four photoreceptor drums for cyan, magenta, yellow and black image formation are disposed in parallel as extending perpendicularly to a sheet transportation direction. The monochromatic toner images of the respective colors are formed on surfaces of the respective photoreceptor drums. In the course of transportation of a sheet along the sheet transportation path, the monochromatic toner images formed on the respective photoreceptor drums are successively transferred onto the sheet. After the transfer of the fourth color toner image, the toner images on the sheet are subjected to a fixation process, whereby a full color image is recorded on the sheet.
Since the tandem image forming apparatus is constructed so that four toner images are successively transferred in superimposition on a sheet, there is a possibility of misregistration of the respective color toner images, which will show up as a color offset in the resulting image.